1. Field of the Invention
The present invention relates to a composition for forming a silicon-containing resist underlayer film and a patterning process using the same.
2. Description of the Related Art
In 1980s, a g-line (436 nm) or an i-line (365 nm) of a mercury lamp was used as an exposure light to be used in a resist pattern forming. As a mean for further miniaturization, a method of shifting to a shorter wavelength of an exposing light was assumed to be effective. As a result, in a mass production process after DRAM (Dynamic Random Access Memory) with 64-megabits (0.25 μm or less of a processing dimension) in 1990s, a KrF excimer laser (248 nm), a shorter wavelength than an i-line (365 nm), was used in place of an i-line as an exposure light source. However, in production of DRAM with an integration of 256 M, 1 G and higher which require further miniaturized process technologies (process dimension of 0.2 μm or less), a light source with a further short wavelength is required, and thus a photo lithography using an ArF excimer laser (193 nm) has been investigated seriously since about a decade ago. At first, an ArF lithography was planned to be applied to a device starting from a 180 nm node device, but a KrF excimer laser lithography lived long to a mass production of a 130 nm node device, and thus a full-fledged application of an ArF lithography will start from a 90 nm node. Further, a study of a 65 nm node device by combining with a lens having an increased NA till 0.9 is now underway.
Further shortening of wavelength of an exposure light is progressing towards the next 45 nm node device, and for that an F2 lithography with a 157 nm wavelength became a candidate. However, there are many problems in an F2 lithography; an increase in cost of a scanner due to the use of a large quantity of expensive CaF2 single crystals for a projector lens, extremely poor sustainability of a soft pellicle, which leads to a change of an optical system due to introduction of a hard pellicle, a decrease in an etching resistance of a resist film, and the like. Because of these problems, it has been abandon the development of an F2 lithography and introduced an ArF immersion lithography earlier.
In the ArF liquid immersion lithography, water having a refractive index of 1.44 is inserted between the projection lens and a wafer by a partial filling manner to enable high-speed scanning, thereby allowing to conduct mass-production of 45 nm node devices by a lens having an NA on the order of 1.3.
Exemplary candidates of lithography techniques for 32 nm nodes include extreme ultraviolet (EUV) lithography at a wavelength of 13.5 nm. Then, exemplary objects accompanying to the EUV lithography are to increase an output of laser, enhance a sensitivity of resist film, enhance a resolution, decrease a line edge roughness (LER), achieve a defect-free MoSi laminate mask, lower aberrations of a reflecting mirror, for example, thereby leaving a pile of objects to be attained.
Another candidate of 32 nm nodes is a high refractive index liquid immersion lithography, the development of which has been abandoned, due to lower transmittance of LuAG as a candidate of high refractive index lens therefor, and due to failure of achievement of a refractive index of a liquid to be increased up to a targeted value of 1.8.
As mentioned above, a photo-exposure method used as a general-purpose technology is reaching an inherent limit of its resolution due to wavelength of a light source. Accordingly, in recent years, an organic solvent development, with which a very fine hole pattern that cannot be accomplished by a conventional patterning process with a positive tone using an alkaline developer is obtained by a patterning process with a negative tone using an organic solvent developer, has been receiving an attention again. This is a process to form a negative pattern by an organic solvent developer by using a high resolution positive resist composition. In addition, investigation is being carried out to obtain twofold resolution by combining two developments of an alkaline development and an organic solvent development.
Usable as an ArF resist composition for development in a negative tone by an organic solvent like this, is a positive ArF resist composition of a conventional type, and examples of patterning processes therefor are shown in Japanese Patent Laid-Open (kokai) No. 2008-281974, Japanese Patent Laid-Open (kokai) No. 2008-281980, Japanese Patent Laid-Open (kokai) No. 2009-53657, for example.
As one method to transfer the thus formed negative-tone pattern to a substrate, multi-layer resist process have been used. The methods are configured to: interpose an intermediate film, for example a resist underlayer film containing silicon atom, having an etching selectivity different from that of a photoresist film, i.e., a resist upper layer film, between the resist upper layer film and a substrate to be processed; obtain a pattern in the resist upper layer film; thereafter transfer the pattern to the resist underlayer film by dry etching by using the obtained photoresist pattern as a dry etching mask; and further transfer the pattern onto the substrate to be processed by dry etching by using the obtained pattern of the resist underlayer film as a dry etching mask.
Examples of silicon-containing resist underlayer films to be used in the above-described multi-layer resist process include silicon-containing inorganic films by CVD, such as SiO2 films (Japanese Patent Laid-Open (kokai) No. H7-183194, for example) and SiON films (Japanese Patent Laid-Open (kokai) No. H7-181688, for example); and films obtained by spin coating, such as SOG (spin-on-glass) films (Japanese Patent Laid-Open (kokai) No. 2007-302873, for example), and crosslinkable silsesquioxane films (Japanese translation of PCT international application No. 2005-520354, for example).